Discrete-element modelling of pile penetration to reveal influence of soil characteristics

Soil response to pile penetration has both macro- and micro-mechanical aspects. At both scales, the properties of the particles and their interactions with each other control behaviour. Unfortunately, examination of particle-scale effects during penetration is not possible with either physical modelling or using continuum-based numerical models. The discrete-element method provides a powerful medium for modelling soils as particulate materials and can be used to investigate pile-soil interaction. However, such models are computationally demanding and need extensive optimisation, which in turn requires an understanding of the influences of soil characteristics on the mechanics. For this purpose, a series of pile penetration models was designed using three-dimensional discrete-element models. Structural parameters such as model dimensions and pile properties were kept constant while the soil characteristics were varied one at a time. This allowed uncoupled observation of the influences of individual soil characteristics including stiffness, inter-particle friction, rolling friction, average size, shape, packing density and grain size distribution. The results are presented in graphical form and their implications with respect to modelling are discussed.